The complete chloroplast genome of Aristolochia hainanensis Merr. (Aristolochiaceae)

Abstract Aristolochia hainanensis Merr. 1922, a well-known Chinese medicinal plant, is distributed in Hainan Province and Guangxi Province, China. In the current study, we sequenced the complete chloroplast genome of A. hainanensis. The complete plastome genome was 159,764 bp in length, with a GC content of 38.8%, showing a typical quadripartite organization. The genome contained a large single-copy (LSC) of 89,134 bp, a small single-copy (SSC) of 19,306 bp, and a pair of inverted repeats (IRs) of 25,662 bp. A total of 113 genes were annotated, including 79 protein-coding genes, 30 tRNAs, and four rRNAs. The trnK-UUU gene contained the longest intron (2644 bp). The topology of the maximum-likelihood tree supported a close relationship between A. hainanensis and A. kwangsiensis.

The Aristolochiaceae are composed of approximately 550 species, most of which belong to a large group in the genus Aristolochia, which includes 450 species (Bliss et al. 2013;Chase et al. 2016;Qin et al. 2021). In the current study, we focused on the species Aristolochia hainanensis Merr. 1922, which is a traditional Chinese medicinal plant mainly distributed in the Wuzhishan Mountain region of Hainan Island. In recent years, with the degradation and loss of their natural growth environment and human harvesting and cutting, A. hainanensis has been listed as a Threatened Species with vulnerable (VU) status on the IUCN Red List (https://www.iucnredlist.org/).
Chloroplasts are important organelles of green plants with roles in photosynthesis and nitrogen fixation (Moore et al. 2007). The chloroplast genome is crucial for the taxonomic classification and phylogenetic analysis of land plants (Moore et al. 2007;Yang et al. 2013;Huang et al. 2014). In recent years, many chloroplast genomes of other species in the genus Aristolochia have been reported, including A. kaempferi, A. kunmingensis, A. macrophylla, A. mollissima, A. moupinensis, A. tagala, and A. tubiflora (Zhou et al. 2017;Li et al. 2019). In the current study, we revealed the chloroplast genome of A. hainanensis for the first time, and aimed to provide basic genetic information harbored in the chloroplast and unveil the phylogenetic position of A. hainanensis.
The complete plastome genome was found to be 159,764 bp in length with a GC content of 38.8%, including a large single-copy (LSC) of 89,134 bp and a small single-copy (SSC) of 19,306 bp separated by a pair of inverted repeats (IRs) of 25,662 bp. In total, 113 genes were annotated, including 79 protein-coding genes, four rRNAs, and 30 tRNAs. Among these genes, 15 contained one intron and three contained two introns. The trnK-UUU gene included the longest intron at 2644 bp.

Ethics statement
The authors have complied with the International Union for Conservation of Nature (IUCN) policies research involving species at risk of extinction, the Convention on Biological Diversity and the Convention on the Trade in Endangered Species of Wild Fauna and Flora. Our study has been approved by local authorities (Hainan Administration of Wuzhishan National Nature Reserve). Lei Liu is the Deputy Director (e-mail: 57019386@qq.com).

Author contributions
Conceived and designed the experiments: RJZ, WG, and MXL. Performed the experiments: MXL, MXF, and HZ. Analyzed the data: MXL. Wrote the paper: MXL. Revised the paper: RJZ, WG, MXL, and MXF. Supervised the project and approved the final version to be published: RJZ and WG. All authors agree to be accountable for all aspects of the work.

Disclosure statement
No potential conflicts of interest are reported by the author(s).

Data availability statement
The genome sequence data that support the findings of this study are openly available in GenBank of NCBI at https://www.ncbi.nlm.nih.gov under the accession no. OL943803. The associated BioProject, SRA, and Bio-Sample numbers are PRJNA795315, SRR17478235, and SAMN24706807, respectively.